FIG. 1 shows a device for measuring the absolute value of the density of salts in atmosphere already invented by the inventor. In the Figure, the reference numeral 7 designates an airtight water tank of a predetermined capacity which contains the super pure water 37 of a predetermined quantity the resistivity of which is above 15M.OMEGA.cm. The tank 7 is made up of a material from which any dissolved material including sodium ions does not soak out, such as a transparent vinyl chloride. The numeral 3 designates a pipe for supplying the super pure water to the tank 7. The numeral 2 designates a valve provided at the pipe 3. The pipe 3 and the valve 2 constitute a means 30 for supplying the water. The numeral 13 designates a bubbling pipe for bubbling the air in atmosphere into the super pure water 37 in the tank 7 to make the salts in atmosphere dissolved into the super pure water 37. The numerals 8, 9, 10, 11, and 12 designate a pipe, a valve, a pump, a flow meter, and a timer, all of which constitute a means 40 for supplying the air in atmosphere to the bubbling pipe 13. The numerals 14a and 14b designate flow switches to hold the level of the super pure water 37 contained in the tank 7 at predetermined levels. The numeral 4 designates an exhaust pipe for exhausting the super pure water 37 contained in the tank 7 to the outside. The numeral 15 designates a valve provided at the exhaust pipe 4. The exhaust pipe 4 and the valve 15 constitute a means 50 for exhausting the water. The numeral 5 designates a sodium ion analyzer for measuring the density of Na.sup.+ ions in the exhausted super pure water of a predetermined quantity. The material taking inlet 5a of the analyzer 5 is sunk in the exhausted water.
The device will be operated as follows:
At first, the valve 2 in the means 30 for supplying the water is opened, and the super pure water 37, the resistivity of which is above 15M.OMEGA. cm, is supplied to the airtight water tank 7 through the pipe 3. When the flow switch 14a, operates, the valve 2 in the water supplying means 30 is closed to stop the supply of the super pure water 37 to the tank 7. Thus, the airtight water tank 7 is filled up with the super pure water 37 of a predetermined quantity. When the valve 9 in the means 40 for supplying the air in atmosphere is opened and the pump 8 is operated, the air in atmosphere is sent to the bubbling pipe 13 through the pipe 8 at a constant flow rate for a predetermined time. The bubbling pipe 13 operates to bubble the air into the super pure water 37 in the tank 7 to make the salts, that is, NaCl in the air dissolved into the super pure water 37. When the bubbling is concluded, the valve 9 is closed, the valve 15 in the means 50 for exhausting the water is opened, and the super pure water in the tank 7 is exhausted to the outside through the pipe 4 at a constant flow rate caused by its positional potential. The sodium ion analyzer 5 with its material taking inlet 5a sunk in the exhausted super pure water operates to measure the density of Na.sup.+ ions in the super pure water. Then, the absolute value of the density of salts in atmosphere is obtained from the density of Na.sup.+ ions in the super pure water measured by the sodium ion analyzer 5 by executing an operation including the mass-conversion between Na.sup.+ and NaCl.
Caused by the exhaustion of the super pure water, the flow switch 14b operates to open the valve 2, and thereafter, the above mentioned measuring operation is repeated. This enables continuous monitoring. In this case, the quantity of the air to be supplied is measured by the flow meter 11 and is regulated by the valve 9. The time period during which the air is supplied can be regulated by the timer 12. Furthermore, the time period during which the super pure water is supplied can be regulated by a means (not shown) provided in the water supplying means 30.
In this device for measuring the absolute value of the density of salts in atmosphere under such construction, however, the background value of the sodium ion analyzer 5, that is, the density of Na.sup.+ ions included in the super pure water 37 before dissolving the air therein is not stable while bubbling. Furthermore, the water tank 7 is not washed while continuously monitoring, and accordingly, the reliability of the measured result is diminished and is influenced by the remaining sodium ions in the water tank 7.